Pasteurization has been used in the wine and brewing industry for many years having been developed around 1865 by Louis Pasteur. Pasteurization is the reduction of microorganisms by heating to a limited temperature and holding at that temperature such that there will be minimum effect on physical stability and flavor and a maximum extension of biological stability, thereby increasing shelf life.
Although the present application describes the invention with reference to the pasteurization of beer, the invention also is applicable to all products which are pasteurized in a package, including soda and other soft drinks, fruit juices and drinks, and milk. The specific P.U. inputs and temperatures and times will vary according to the product being treated.
The various organisms in beer are not pathological and dangerous to humans, but affect the taste and appearance of the beer if allowed to grow. Draft beer generally is not pasteurized because it is kept refrigerated and is usually consumed in a short time. However, high quality can and bottle beer traditionally is pasteurized for long shelf life, and conventional type pasteurizers are shown in Herold U.S. Pat. No. 2,282,187 issued May 5, 1942 and Wehmiller U.S. Pat. No. 2,658,608 dated Nov. 10, 1953. Other patents showing pasteurizer and pasteurization processes pertinent to this invention include Becker U.S. Pat. No. 4,441,406, Huling U.S. Pat. No. 4,263,254, Huling U.S. Pat. No. 4,279,858 and Huling U.s. Pat. No. 4,331,629.
In this type pasteurizer, water is sprayed onto the tops of the closely packed packages which are moved through a tunnel which is divided into preheat zones, heating zones, holding zones, and cooling zones. The temperature of the beer in the containers is progressively raised to the desired level before being passed through the cooling zones where it reaches the desired beer out temperature (BOT). The water running off the packages is collected in reservoirs, heated or cooled, and recycled to the sprays or spray pans. These types of tunnel pasteurizers are available in single and double deck configurations.
If pasteurization causes the temperature of the beer to reach too high a level, certain tastes called "pasteurization tastes" can occur in the beer. These are undesirable and have been defined as "bready", "biscuity", "burnt-type tastes", "papery" or "cardboardy". Also, insufficient pasteurization can result in turbidity of the beer or sedimentation.
The organisms which cause the most difficulty in the brewing industry today are actobacillus, pediococcus and wild yeast. These are not pathogenic organisms but can cause turbidity and poor taste in beer. In order to insure complete pasteurization of beer, the temperature of the beer at the so-called "cold spot", which is 1/4" from the bottom of the center of the can or bottle, must reach at least 140.degree. F. for a period of time to produce a specified number of pasteurization units (P.U.). It also is desired to pasteurize at the lowest possible peak cold spot temperature (above 140.degree. F.) to avoid overheating the rest of the package contents, because the temperature of the package gets higher as one goes from the cold spot to the top of the package.
The P.U. is a measure of accumulated lethality. One P.U. for beer is one minute at 140.degree. F. Lethality (P.U. per minute) is a rate term which is exponential with temperature. Lethality begins to become significant only when the beer temperature is 130.degree. F. to 135.degree. F. and is most significant at 139.degree. F. and above, although P.U. accumulation begins at 120.degree. F.
Richmond et al. U.S. Pat. No. 4,693,902 describes a process and apparatus for pasteurizing packaged products, specifically beer, with a high spray density and a uniform spray density across the width of the pasteurizer tunnel. The present invention is an improvement on this process in that the variables which go toward determining the P.U. input to the packaged product are monitored and reported to the pasteurizer operator on a predetermined regular basis. The basic processes and apparatus of U.S. Pat. No. 4,693,902 are utilized, but instead of using the conventional P.U. measuring device, continuous readings of the spray water temperature and the speed of the packaged product through the line are recorded and the P.U. is calculated continuously as the product exits the pasteurizer tunnel.
The conventional P.U. measurements device or "P.U. Box" consists of a container having a thermometer wired therein which is connected to a recorder. The wired container is sent through the pasteurizer tunnel and the beer cold spot temperatue is recorded as it progresses through the tunnel. Using the beer cold spot temperature and time, P.U. input is calculated.
This method of measuring P.U. takes approximately 25 minutes to run a can and about 45 minutes to run a bottle through the pasteurizer. The set up time results in a total of only four P.U. Box runs being made through a pasteurizer in an 8 hour shift. The reading also is accurate only for those containers in the same line across the width of the pasteurizer as the P.U. Box container. Thus, only about 500-1000 of approximately 500,000-1,000,000 cans which run through the pasteurizer in an 8 hour shift can be tested and verified for proper pasteurization. Additionally, even though 4 P.U. Box runs per shift per machine are theoretically possible, the manpower required to run this test 4 times per shift around the clock makes it economically unfeasible. Normal testing is only one or two runs per machine per week.
Therefore, instead of less than even 0.1% of the packages being measured for P.U. content (the current practice), this invention provides substantially 100% P.U. measurement and pasteurization verification for the packages leaving the pasteurizer.
Additionally, under the conventional system, pasteurizer conditions are set arbitrarily based on operating experience to obtain the desired pasteurization results. These settings are always conservatively high in an attempt to allow for unexpected problems such as pasteurization down time, unstable temperature control, and although unknown at that time, non-uniform non-optimum spray density, etc., which would adversely affect and change the P.U. input to the product leaving the pasteurizer. These settings are then checked by running a P.U. Box through the pasteurizer at steady state normal operating conditions to verify that normal operation gives the desired pasteurization. This system provides no way to check or verify results under abnormal conditions and, in fact, it is rare if the exact time and circumstances of the abnormal occurrences ae even known.
The P.U. Box system also is subject to operator ability and mechanical failure such as bent probes, the location of the sample in the box, partial "run-out" during the P.U. Box run, down time and low battery charge. A 5 minute down time can add 7.5 P.U.s to the packages.
In the conventional measuring method, it is not unusual for the run of an entire 8 hour shift to be impounded and checked for P.U. input. This requires taste testing or holding the product for a period of up to seven days to determine if anything adverse happened to the packaged product. The checking involves plating, check for turbidity development, etc. With the present system it is easy to identify a specific part of a run that may be adversely affected by the pasteurization conditions and then it is only necessary to isolate that small part of the run for testing. Also, one can recall the data for that portion of the run and recalculate the data if a setting was incorrect for the type of container, etc.
The present process also provides for calculation of the maximum cold spot temperature, which in the case of beer, must reach 140.degree. F. for a minimum of 1 minute to be sure that all portions of the container have been heat treated adequately for pasteurization.
The present process also provides for recording and reporting of the average product out temperature as the product is leaving the pasteurizer. This is important because it is desirable to maintain the product out at approximately the ambient dew point temperature which will avoid condensation forming on the product container which adversely affects the packer process.
Accordingly, it is a principal object of the present invention to provide a process for continuously monitoring a tunnel pasteurization line by continuously monitoring the water spray temperature along the length of the tunnel and monitoring the speed of the packages through the tunnel and using this data to calculate and report the P.U. input, the maximum product cold spot temperature and the average product out temperature of the packages leaving the tunnel at preselected time intervals. It is another object of this invention to record all of this raw data and to be able to retrieve said data at a later time if the operator needs it to determine malfunctions of the pasteurizer.
It also is an important object of this invention to provide a computer system configuration and software approach for implementing the data measurement and storage, data retrieval for calculations, graphical presentations, and automatic report generation for all levels of management.
It also is an object to provide a historical data retention and recall program for repeat presentation and diagnostic procedures as required.
It is also an essential object of this invention to provide the heat transfer data necessary to make the calculations of temperature change versus time in the pasteurizer.
These and other objects and advantages will become apparent hereinafter.